Sparks

The renewables in ourselves

 By Amanda Saint

In the renewable energy world, researchers are always looking for innovative ways to create cleaner power. One of the more recent sources they are looking into is using body heat for energy. But how viable is this as a reliable source of energy for the future?

There are already some pretty large-scale projects that are using body heat to create electricity and warm buildings, plus there are residential homes being built that use only the heat generated by people living in them. On a smaller scale, body heat is being seen as a great energy source to power consumer electronics.

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How body's energy heat works (goos3v1, favpng.com)

Stockholm rail station

In Sweden, Stockholm’s Central Rail Station channels the body heat generated by 250,000 daily commuters into a nearby office building to supply heat without using fossil fuels. Although the body heat generated in buildings where large groups of people congregate has been used in situ to cut the energy used for heating, the Sweden rail project was one of the first to take the heat generated and use it elsewhere. The project was led by real estate company called Jernhusen, which came up with the idea of using the commuters’ body heat to warm water stored in underground tanks beneath the station. This heated water is then pumped into the heating system of a neighbouring office block, resulting in the use of less energy to create the heat it needs. In total, the body heated water has enabled the office building to use around 25% less energy for heating.

The Mall of America

In Minnesota, which has an extremely cold winter climate, the Mall of America has no central heating at all and relies purely on renewable energy to maintain a comfortable temperature. This comes from a combination of heat sources generated through skylights, tapping into the heat generated from the fixtures and lighting in stores and restaurants, and using the body heat of the 40 million+ shoppers that visit each year. All these components keep it warm when outside temperatures often fall as low as -10 degrees Celsius.
Using these sources of heat, the mall—which covers more than 4.8 million square feet—is able to maintain a year round temperature of 70 degrees Celsius no matter what the weather is doing outside.

London underground

In the UK, a new body heat energy project that will be live from Winter 2019-2020 will be using the heat generated by commuters and trains on the underground rail system’s Northern Line to feed into a district heating system for the London Borough of Islington. The energy created by this heat will be used to warm 1,350 local homes as well as office buildings and leisure centres.

(uk.ramboll.com)

The heat the project will be capturing was previously expelled through a ventilation shaft in a closed-down station. Now it will be rerouted into the district heating system and put to use. This is the first of many projects the city has planned that will tap into waste heat. Research carried out by the Greater London Authority revealed that if captured and reused, such heat could provide up to 38% of London’s heating.

Electronic gadgets

There’s much research into how our body heat could be used to power small electronic gadgets. At the University of Massachusetts, for instance, scientists have been working on a fabric that converts body heat into electricity to power wearable electronics such as fitness trackers. They’ve built on the natural insulation and conductivity properties of wool and cotton to create the non-toxic fabric they say could be adapted by device engineers for efficient renewable energy generation for wearable electronics.

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A prototype of a fabric capable of storing body heat (University of Massachusetts)

Meanwhile, researchers at Texas A&M University have been focusing on how the excess body heat created when exercising could be harnessed to power other electronic gadgets. The team’s research has been focused on how carbon nanotubes can be used to capture body heat for reuse as energy; they believe in the future they will be able to develop shirts that can recharge cell phones while the wearer is exercising. At the North Carolina State University, a team of engineers have designed a flexible thermoelectric energy harvester that relies purely on body heat to power it. Designed for future use in devices that can be used to track people’s health data, such as blood pressure and blood sugar, heart rate and heart beat, this innovation has been driven by the desire to make flexible body heat harvesters as efficient as rigid ones. By using a non-toxic alloy called EGaIn, which is comprised of a liquid metal of gallium and indium, the researchers say they have achieved it.

Viable and reliable?

So, will these kinds of projects be able to provide a viable and reliable renewable energy source in the future? Large scale projects like those at the Mall of America and Sweden and London’s train stations are definitely forerunners of more projects that can harness waste heat for energy. The wearable devices are still in the very early stages, but as our understanding of ways to harness body heat and develop the right conductive materials to make use of it grows, there is no doubt these will be available to consumers in the future. As Forbes Magazine puts is, the human body has the potential to be a renewable energy plant—both on its own and as part of a crowd.

READ MORE: The road to 100% renewable energy by Robin Wylie

about the author
Amanda Saint
Journalist and content writer, specialised in engineering and technology with a focus on environmental sustainability, urbanisation and biotechnology.